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Agriculture in South Africa plays a critical role in the formal economy, in sustaining rural livelihoods and in food security. Climate change has clear implications for both the large and small-scale agricultural sector, and is the subject of sectoral strategies currently in draft. As the science evolves, the science-policy community is actively working to translate the science of agriculture and climate into response and action, in partnership with farmers.
The agricultural sector is likely to feel the direct and indirect impacts of projected climatic changes in a number of ways. Firstly, predicted higher temperatures are likely to negatively impact organic matter; in an environment where retention of organic matter in soils is already affected by other stressors, such as grazing, addition of fertiliser and manure, burning, and soil cultivation (Reicosky et al., 1995)
Secondly, the predicted increase in evaporation has critical implications for irrigated and dryland agriculture, as well as the full range of livestock farming systems. For example, increased temperatures and resulting evaporation are likely to increase irrigation demands, in a country where existing water supply and quality difficulties provide stress already to the irrigated agriculture sector (again, affecting both large-scale and emerging agriculture).
Livestock farming systems are affected by higher temperatures and evaporation rates (Table 1), by, for example increasingly exceeding the temperature thresholds above the thermal comfort zone which could induce behavioural and metabolic changes including altering growth rate, reproduction and ultimately mortality (Batima et al., 2006). Lawless (2007) shows for South Africa's summer rainfall semi-arid savanna rangelands that increases in the Temperature-Humidity Index (THI) under climate change (using version 1 downscaled climate change projections) will more frequently exceed the thresholds of comfort for commercial stock identified in the literature. Such a finding is particularly concerning since even no change, or an increase in rainfall and accordant possible improvement in forage availability may be offset by THI increases and consequent negative effects on stock condition and morbidity/mortality rates. Conversely, increases in temperature during the winter months can reduce the cold stress experienced by livestock and warmer weather could reduce the energy requirements of feeding and the housing of animals in heated facilities (Beyene 2009). In addition, certain breeding trends in livestock production may have increased vulnerability to heat stress (and pests and pathogens), as certain breeds have been produced for high production, often compromising hardiness and thermoregulation. Higher temperatures and evaporation rates also affect stock water requirements. As in the irrigated sector, this is particularly concerning in an environment where water requirements for agriculture are already under threat.
Table 1: Summary of possible impacts of climate change on livestock production systems (after Beyene 2009).
| Direct livestock impacts |
- Changes in forage quality and quantity
- Changes in the length of the growing season
- Changes in water quality and quantity
- Reduction in livestock productivity
- Increased prevalence of 'new animal diseases
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| Indirect livestock impacts through ecological impacts |
- Increased frequency of disturbances, such as wild fires
- Changes in biodiversity and vegetation structure
- Changes in soil nutrients
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| Socio-economic/livelihood impacts |
- Changes in incomes derived from livestock production
- Shifts in land use (including consequences of land reform)
- Overall changes in food production and security
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The projected increase in rainfall intensity, as mentioned earlier, indicates a likely increase in drought potential. All agricultural systems in South Africa are likely to be affected by such an increase. In staple crop farming, for example, drought at particular points in the growth cycle affects yield and quality. In high value vegetable farming, increased drought potential affects quality, yield and sustainability of supply. In fruit farming, quality, supply and sustainability of supply would also be affected; potentially compounded by projected challenges in water availability and supply mentioned elsewhere.
Lastly, higher temperatures may favour the spread of pests and pathogens of significance to a range of agricultural systems. For example, a number of pathogens of concern to the high value vegetable and fruit industries prefer higher temperatures. A number of research institutions are currently partnering to understand precisely how this may cause a challenge to the affected industries.
Given the projected areas of concern described here, the response of the agricultural sector is key. It is possible that the sector may have to think very differently about production, incorporating soil, water and nutrient conservation practices that produce a range of benefits simultaneously, as well as improving response to climate change. It is likely that such an approach may include a move to more sustainable and resilient livestock and crop and high value product systems. What constitutes a resilient system must be the focus of ongoing and urgent investigation, to better inform recommendations and support provided by the Department of Agriculture, Forestry and Fisheries in this regard (the Department's sectoral strategy is currently in draft).
Such an approach might also include, particularly post the Copenhagen negotiations, the inclusion of carbon sequestration and diminished greenhouse gas emissions as one of the multiple benefits management objectives of the agricultural sector. Incentives available to the sector will be of particular interest in this regard.
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